I am sure you could find somewhere around there, but the Bentota area is better known for its big star class hotels. You'd get a better choice of value guesthouses if you looked around Hikkaduwa which is half way between Galle and Bentota.
There's a turtle hatchery around there too. Go to the one at Seenigama which is just north of Hikkaduwa town .. just a few rupees and a couple of minutes on the local bus. Make sure you only release baby turtles at the very end of the afternoon/early evening, because at all other times, they will be picked off by predators. When we went to this hatchery, we were assured that they only release them late in the day, but I'd be keen to know if this is still the case, because I will tell people to go elsewhere in future if the baby turtles' welfare isn't considered. There was no charge for admission or for releasing baby turtles at the Seenigama hatchery, but donations were encouraged to enable them to continue with their work.
-:- Message from TripAdvisor staff -:-